This invention relates in general to casting machines and in particular to a method of controlling the filling of a mold cavity of such a casting machine with molten metal.
Pressure pouring of molten metal from a furnace to fill a mold cavity has been used for several decades despite a number of problems. At room temperature, the metals are solid and become fluid when melted with sufficient heat. When the metal becomes a fluid it can become difficult to manage as it begins to assume fluid dynamic characteristics.
It is known to use a low pressure countergravity casting apparatus to cast molten metal into mold. One example of such an apparatus is described in U.S. Pat. No. 5,215,141. Basically, in a low pressure countergravity casting apparatus molten metal is supplied to a reservoir of a casting apparatus by a metal supply furnace. The molten metal is received into a crucible of the casting machine. The molten metal is then transported to a holding chamber through a feed tube placed into the crucible. A mold, typically mounted on the holding chamber, receives the molten metal into a cavity of the mold through holes in the mold.
The basic problem in managing the molten metal has been monitoring and controlling the numerous variables which affect the flow of the molten metal in a cavity molding system. These variables effect, among other things, initiation of the molten metal flow, velocity of the molten metal flow, acceleration of the molten metal flow, stopping the flow of the molten metal, and slowing down the molten metal flow within the system. Much of the problem is the number of variables involved and interactions between them, that will effect this complicated and integrated fluid dynamic system. Some of the difficulty is due to variations in the ability to measure the fluid dynamics within the system. Some of the difficulty is due to the ability to control the dynamics within the system once the measurements have been made. Thus, it would be desirable to provide a process to identify and measure the variables which influence molten metal fluid dynamics and control the flow of molten metal within the cavity molding system which is simple and reliable.
This invention relates to a method for producing a cast article comprising the steps of: (a) providing a casting apparatus having a mold, a casting chamber containing a molten metal under pressure and a fluid under pressure, the casting apparatus having a first supply port for supplying the molten metal to the casting chamber and a second supply port for supplying the fluid to the casting chamber; (b) supplying the molten metal to the first supply port; (c) supplying the fluid to the second supply port; (d) determining the amount of the molten metal in the casting chamber as a variable V1; (e) determining the amount of the fluid in the casting chamber as a variable V2; (f) determining the amount of humidity in the casting chamber as a variable V3; (g) determining the amount of the fluid entering the casting chamber as a variable V4; (h) determining the pressure of the fluid in the casting chamber as a variable V5; (i) determining the amount of the molten metal needed to produce a cast article in the mold as a variable V6; (j) determining the change in the pressure of the molten metal in the mold as a variable V7; (k) sensing the position of the molten metal with respect to the mold as a variable V8; (l) providing a control panel, wherein the control panel receives a signal representative of the variables V1-V8; and (m) adjusting the supply of one or both of the molten metal or the fluid in response to at least one of the signal representative of the variables V1-V8.
Other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.